Wossner Xu9J4 Pistons In An Xu9Ja Engine.

[opticaltrigger 52]

Hi All

Thought I would do a quick post on the issues encountered while trying to use a set of Wossner XU9J4 pistons in our XU9JA turbo project in case anyone else has tried it and had the same problems.

 

It's not been straight forward at all.

 

Firstly the only similarity between the two has been the bore size,after that we were on our own.

 

The compression height on the XU9J4's is 38mm requiring 1mm to be machined off to match the 37mm of the XU9JA engine.

The XU9J4 pistons should be machined to guide the rod by the piston but there not.It's machined the same as the XU9JA where the rod is still guided by the crank.(This was not really a problem for us though).

And finally while doing a dry build last weekend we discovered that the bottom of the pistons hit the crank counterweights at BDC requiring the pistons to be machined 1.5mm to clear.(Hopefully)

 

What Iv'e deduced from this is that either Wossner supplied us with rouge pistons where the only correct measurement is the bore size or this is just what you get when you use them in an XU9JA engine.

The difference in compression height I am fine with but the odd small end rod clearance and the underside of the piston hitting the crank at BDC strikes me as very strange.

 

Does anyone out there know more about this so that I can better understand what's going on with them ?

 

All the very best

O.T.

 

[dcc 855]

I understand from experiences of many people that wossners are basically a false economy. Badly machined and nowhere near accurate enough to use in a well built engine.

 

The old saying is buy cheap buy twice

[petert 589]

Not sure were your deck heights are coming from. The theoretical XU9 compression height is 37.50mm. A height of 38 would have the piston sit 0.5mm above the liner. Most XU9 engines are 37.12mm. The DFW is 36.2 (from memory) and the DFZ is 37.50mm.

[welshpug 1,661]

if they're hitting the crank in an 8v block I dread to think what they would do to the spray bars in the 16v block.

 

other than that there shouldn't be any difference.

[opticaltrigger 52]

I think you guys have spelled it out for me really. There just not right are they.

I explained all of this to the supplier (GMC Motorsport in Scotland) and they obviously either did not listen or did not care.

 

The kit took 600 years to arrive and when it did it came with a broken second ring. GMC assured me that it was me that broke the ring and basically said pay again. Even paying again did not help as the ring set never arrived so I tried TSR in Bridgwater who were about as good and only suggested either keep waiting or shop elsewhere. And finally I ordered them from Wossner America who shipped them out immediately via UPS for a Kings ransom.

 

I wrote an email to Wossner in Germany who still have not replied properly as yet. What a joke, in 2015 you cant call, email, or otherwise contact a major global piston supplier.

 

I get the feeling that how all this works is. The UK Wossner agents are private businesses doing there own business and if they have time they will order something from Wossner for you eventually. I can imagine that they probably originally got into being agents because it meant they could get pistons cheaper for there own work and stuff you mate after that.

 

Anyway as always you guys have helped me out loads again with your advice. Many thanks.

I will try again tomorrow to fit them in the block and see what happens. Will do a progress update on the problem. You never know, I might even here back from mysterious Wossner eventually.

It would have been cheaper, quicker, and easier to have had them made to order by JE in the states.Those guy's don't mess around. Europe......Jokers.

 

NEVER, NEVER, NEVER EVER USE WOSSNER PISTONS or Wossner anything is my new moto.

 

All the best gents and many many thanks again for your input. Invaluable.

O.T.

[petert 589]

Mmmmm........now you've got me worried. I bought these custom 2 ring Wossner pistons from a guy over here who'd planned a big build but had to sell up. I got these and the matching rods at a great price but maybe I should have just stayed with the original plan.

[Sandy 191]

I'm sorry to hear the trouble you've had, but glad you've posted about it. I've felt like a bit of a lone voice on this subject (mostly around the TU engine fitments) and often have to defend my reasoning for not using or recommending using their products (let alone the "PEC" rods, which are very poor design in these applications). The margin is good and trade price about half of what I pay for the CPs I have made for my engines, that and supposedly "off the shelf" availability (often not the case) are why so many companies favour using them and that proliferation gives people confidence. It is possible to supply badly designed, machined and treated products in this market, being able to hide behind "motorsport use" as a caveat for any problems. Buyer most certainly beware.

[opticaltrigger 52]

Hi Gents,

Well I went over to the engine today and fitted up the pistons into the block and the clearance that was machined under them did the trick and there in now and clear the crank adequately.

 

It's just great that there in and done because honestly I really cant put into words what a stress it's been and how long it's taken. I actually ordered those pistons at the beginning of April and only today did they get installed in the engine. Wow!!!.

 

I am now convinced above all doubt that the pistons were machined inaccurately because there are just to many errors. Some of the errors are large ones like the small end clearance and some are more subtle like the area on the underside that was hitting the crank.

I feel almost like I've come to the end of a great quest with them.

 

I completely understand your concerns Pete, I really do but I can only hope that you don't also have the same stress with them mate.

Oh, also, just for the record I now hear that the Wossner rods are actually made in China which doesn't necessarily mean a negative but I think it's interesting enough to note though.

 

Sandy, I think your comments are absolutely bang on and I also agree with your thoughts on the PEC stuff to.

Reading between the lines I have the feeling that Wossner have done a tremendous piece of marketing where they have managed to convince the market that they are a big quality company with quality products when the truth is very different from that.

The fact that despite exhaustive efforts and months of trying I have as yet been unable to speak to Wossner either on the phone or by email makes me feel that they are not the same company that the image portrays.

 

Very, very badly made components supplied by a manufacturer with very little concern for customer service. Terrible, and I will never ever use them willingly again.

As Sandy put so well above. "Buyers most certainly beware".

 

Anyway all the very best guys and I hope that others can avoid all this in future.

O.T

Edited October 25, 2015 by opticaltrigger

[welshpug 1,661]

most of the issues come from the design stage not machining, you just have to compare the rods against even a standard type let alone a carillo or Farndon etc and the weaknesses are glaringly obvious.

 

thankfully it seems you are on the right tracks at least, amd concretes the reasoning behind a dry build before final assembly.

[opticaltrigger 52]

Hi welshpug,

Yes, totally agree. I get the feeling that materials wise there probably ok but the design / machining is very very bad indeed.

 

All the best

O.T.

[Miles 331 1 Cars]

Had issue's with getting rings for the pistons from a rebuild of a customers engine, around 8 weeks later and the right ones turned up, Also had a buy a set for a T16 engine but so far so good but it's not something I would normally use, I tend to favour JE which I use in mine and have done me proud to date

[petert 589]

I'm lucky that mine will be fine for a hand grenade engine for myself, and I don't expect much more.